<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title></title>
</head>
<body>
<script>
//    (function test(){
//        var a=b=5;
//        alert(typeof a);////number
//        alert(typeof b);////number
//    })();
//    alert(typeof a);//undefind
//    alert(typeof b);//number为什么是number

    var i = 1
    for(var j = 0; j < 3; j++){
        i = i++
    }
    console.log(i)
</script>
</body>
</html>